Mechanical interlock



NOV. 1, O TAYLOR MECHANICAL INTERLOCK Filed 001;. 25 1951 2 Sheets-Sheet 1 Fig.1.

I l P Q j 20 2o" 22' WITNESSES: INVENTOR 542 42 Ow en L.Toylor. 2% Z ATTORN EY Nov. 1, 1955 o. L. TAYLOR 2,722,135

MECHANICAL INTERLOCK Filed Oct. 25, 1951 2 Sheets-Sheet 2 Fig.2.

H' I ,m

WITNESSES: INVENTOR Owen L.T0ylor.

255m MEW ATTORNEY United StatesPatent Office MECHANICAL INTERLOCK Owen L. Taylor, Easton,

Electric Corporation, tion of Pennsylvania Conn., assignor to Westinghouse East Pittsburgh, Pa., :1 corpora- This invention relates generally to interlocking mechanisms for interlocking the movement of two relatively movable members or devices. More in particular, this invention relates to an interlocking mechanism adaptable for interlocking a pair of switches.

Mechanical interlocks on reversing and multi-speed line starters and contactors are often required to properly operate an electrical system. There are two important reasons for such interlocking. First, it must be impossible to have the line contacts of both switches make circuit simultaneously under any conceivable set of circumstances. Second, under the most severe possible coil control cycle the time interval between the openings of the line contacts on one switch and the closing of the line contacts on the other switch must be Sllfl'lCiCIlt for the arcs on the contacts of the opening switch to always extinguish before the closing contacts make circuit. Failure to achieve a sufiiciently long time interval leads to shortcircuiting.

For many switch designs, a simple bar pivoted at the center and connected with the moving components of both switches, may be adjusted so that when one switch is sealed or closed, the other is locked in the full open position. An arrangement such as this will prevent the switches from making contact simultaneously. This type of interlock for switches having high inertia moving parts and large magnet gap to overtravel ratio will allow sufficient time for the arc to extinguish when one switch is open before the other switch closes the circuit.

However, present designs of relays, contactors, and line starters for use on alternating current circuits, tend toward small, low inertia parts, relatively high speed magnets, and small magnet travel as the overtravel approaches the open gap distance of the switch contacts. The straight bar type of interlock, mentioned hereinabove becomes impractical because the time interval during which the contacts of both switches are open is very short and the are on the opening switch may not be completely extinguished before the contacts on the closing switch engage.

The foregoing considerations indicate that a non-linear relationship in the interlocking mechanism is desirable.

One object of this invention is to provide a mechanical interlock for switches and other relatively movable devices which is simple in its elements with respect to operational requirements and positive in operation and which may be cheaply manufactured and assembled.

Another object of this invention is to provide a mechanical interlock for a pair of relatively movable devices or switches which is operative to lock one device or switch in a given position substantially immediately when the other device or switch is moved in a given direction.

A further object of this invention is to provide a mechanical interlock especially adapted for interlocking a pair of switches which is effective to substantially immediately lock one switch in open position when the other switch is moved toward closed position and which effects a reversible non-linear relationship in the relative movement of the moving components of the switches.

2,722,135 Patented Nov. 1, 1955 A specific object of this invention is to provide a mechanical interlock of the character referred to which is adapted for interlocking switches mounted one above the other.

The foregoing statements are merely illustrative of the various aims and objects of this invention. Other objects and advantages will become apparent from a study of the following specification when considered in conjunction with the accompanying drawings in which:

Figure 1 is a plane View of a switch interlocking system embodying the principles of this invention,

Fig. 2 is a side view partially in section of the interlocking mechanism illustrated in Fig. 1,

Fig. 3 is a detail sectional view taken Ill-III of Fig. l, and

Fig. 4 is a fragmentary detail indicating a modification of this invention.

In the interest of simplicity, the switches which are interlocked by the mechanism of this invention are illustrated only in dot-dash outline, inasmuch as the switch details are not essential to an understanding of this invention. The switches 1 and 2 are adapted for mounting on a panel in vertical relationship, that is one above the other, as viewed in Fig. 1. In Fig. 1 each switch is provided with an arm 3, also shown in dot-dash outline, which follows the movement of the operating member of the switch between closed and open positions or, alternatively, may be used to operate the switch. A member such as 3 is also effective, if prevented from moving to hold the switch in its open position.

Switches 1 and 2 are mechanically connected by an interlocking mechanism, generally designated 5. This interlocking mechanism comprises a pair of similar lever systems, generally designated 6 and 7. The upper lever system 6 comprises an assembly which is mounted upon a bracket 9. This bracket is adapted for mounting on suitable pads such as 10 (see Fig. 2) secured upon the panel which mounts the switches 1 and 2. The bracket 9 is blanked from a single piece of sheet metal and thereafter formed by bending to the configuration shown. The bracket is secured to the switch panel by means of a pair of screws 11, which thread into the face of the panel to secure the bracket 9. Part of the bracket at 12 (see Fig. 2) which is bent outwardly from the bracket base, forms a support or bearing mount for a lever 14, which is pivotally mounted adjacent the extremity of this support by means of a pin 15 or other suitable device for pivotally mounting lever 14.

As viewed in Fig. l, the left hand end of the lever 14 is forked and the side arms of the fork straddle the member 3 of switch 1. The right hand end of lever 14, as seen in Fig. 1, has pivotally mounted thereon a locking link 17, as shown. The outer end of this locking link is secured by a pin 18 to the right hand end of the lever 14.

The bottom end of the bracket 9, as shown in Figs. 1 and 2, is bent outwardly from the panel and is provided with a leaf spring mounting support 20. A leaf spring 21 which is substantially L shaped, is secured at one end to the spring support 20. This mounting is acomplished by clamping the mentioned one end of the leaf spring between the spring support 26 and a plate 22 having two clearance holes for rivets 23 therein. The free end of the leaf spring 21 projects upwardly beneath the free end of locking end 17, at which point it is provided with a notch 25. The free end of locking link 17 has a V-shaped notch cut thereon, as shown at 26, the bottom of this V-shaped notch engages the bottom of the notch 25 in the leaf spring 21.

The mechanics of the construction will be better understood by referring to Fig. 3. In Fig. 3, line 28 is a center line between the pivot pins 15 and 18 on lever 14. Pin 15 forms the pivot about which angular moveon the line ment of lever 14 occurs. Pin 18, is the pivot about which the locking link 17 angularly moves on the lever 14. Arrow 30, which is drawn through the axis of pin 18 in a position perpendicular to the center line 28, represents the line of action of the force applied to locking link 17 upon angular movement of lever 14 in a clockwise direction. 'As viewed, spring 21 occupies a position between pivot pins 15 and 18 and is so positioned that its minimum cross-sectional dimension is disposed laterally of the assembly and its maximum cross-sectional dimension is disposed vertically of the assembly. Thus minimum spring stiffness lies in a lateral direction and maximum spring stiffness lies in a vertical direction. Clockwise angular movement of lever 14 due to movement of the arm 3 when the associated switch is moved to closed position, results in the application of a force to the link 17 at pivot pin 18, which for the instant position of lever 14, is in the direction of the arrow 30. A component of this force acts longitudinally of the link 17 and due to the stiffness of leaf spring 21 vertical movement of lever 14 clockwise results in deflection of leaf spring 21 towards the left, as seen in Fig. 3 and also as seen in Fig. 1. It will be appreciated by reference to Fig. 3 that a non-linear relationship exists between movement of leaf spring 21 and pivot pin 18 and consequently also exists between pin 18 and the lever 3 of the associated switch, since, as pivot pin 18 moves circumferentially leaf spring 21 is displaced linearly. At the normal position of the lever assembly which is illustrated in Fig. 3, movement of pin 18 through a given circumferential distance will affect greater linear displacement of leaf spring 21 than will be affected for the given circumferential displacement of pin 18 at the time lever 14 approaches its limit of clockwise angular displacement. In efiect, the arrangement is a modified application of simple harmonic motion.

' The lower lever system 7 associated with the switch 2 is identical in all respects to that of the system 6 as thus far described. Accordingly, parts of the system 7 corresponding to parts of system 6 have been given like reference characters which are primed and the explanations made in connection with lever system 6 may be read also on the lever system 7.

The transmission of the motion of leaf springs 21, 21', and/or links 17, 17, from one lever system to the other is accomplished by means of a lever arm 33 which is substantially centrally pivoted by a pivot mounting, generally designated 35. This pivot mounting is secured to the switch panel permitting clockwise and counterclockwise movement of the lever arm 33 thereabout. The ends of lever arm 33 are hook shaped, the uper hook 33a being inwardly formed and the lower hook 33b being outwardly formed, to adapt the respective ends for engagement with the free extremities of the leaf spring 21 and 21, respectively.

It will now be appreciated that operation of the upper switch 1 to closed position (see Fig. 1) will actuate the leaf spring 21 through the lever 14 and link 17 to the left, as viewed. Displacement of leaf spring 21 to the left applies a counterclockwise force to the lever arm 33 at the hook 33a and the lever arm is angularly displaced in a counterclockwise direction in a degree depending upon the displacement of leaf spring 21. The hook 33b at the bottom end of lever arm 33 which bears against the upper end of leaf spring 21 forces this leaf spring to the right as viewed in Figs. 1 and 3. This displacement, assuming the arms of lever arm 33 are equal in length, will correspond exactly to the displacement of the end of leaf spring 21. As seen in Figs. 1 and 3, leaf spring 21 is moved to the right angularly displacing the locking link 17' in a direction towards the line of action of a force, represented by arrow 30, which may be applied to the upper end of link 17 if an attempt is made to close the switch 2 at this time. Movement of locking link 17 in a counterclockwise direction towards line of. aCliQIl 30,

greatly increases the mechanical advantage of the locking link and leaf spring in resisting forces applied to the locking link at pivot point 18. The assembly does not move to full locking position but moves sufficiently that attempts to close the switch 2 either manually or by some automatic means are ineffective because the transmission of force through this substantially locked lever system is insufficient to overcome the holding force of the lever system 6.

Should it now be desired to open the switch 1 and close the switch 2, suitable means not shown are operated to effect this operation. As the switch 1 opens, lever 3, which follows the movement of the switch operating member, moves out of the plane of the drawing as shown in Fig. l, pivot point 18 now moves through a substantial arcuate distance but due to the position of link 17 permits only a relative small displacement of the end of leaf spring 21 towards the right. Thus the switch mechanism of switch 1 moves substantially to full open position during this interval of small return displacement of leaf spring 21. Referring to the lever system 7 it will be appreciated that throughout this movement back to normal position of the lever arm, which is now following leaf spring 21, and substantially no displacement of the pivot pin 18' occurs and the switch 2 is yet held in full open position when the linkage reaches its neutral position illustrated in Fig. 1. The switch mechanism of switch 2 is then effective through the linkage system to reverse the positions of the lever systems at this time. Operation, the reverse of that hereinabove described,

occurs.

In order to compensate misalignment of certain of the parts due to manufacturing tolerances the pivot mounting 35 of lever arm 33 is pivoted with a degree of eccentricity to effect lateral displacement of the lever arm for adjustment purposes.

Longitudinal displacement of the lever arm 33 over small distances is not objectionable due to the degree of overlap of the ends of the hooks 33a and 33b with the respective leaf springs 21 and 21'. However, improper positioning of the point of the lever arm 33 in a lateral direction may result in the hooks 33a and 33b not engaging the respective leaf springs or may result in the hooks deflecting the leaf springs to the right in too great an amount, if the pivot for the lever arm is located too far to the left or to the right, respectively. To compensate this, the post 36 of pivot mounting 35 is provided with a cylindrical shoulder 37 at the left hand extremity thereof as viewed in Fig. 2. A hole 38 is formed longitudinally of the post in an eccentric position with respect to cylindrical shoulder 37. The hole 39 in the center of lever arm 33, about which the lever arm turns, fits over the cylindrical shoulder 37 and the depth of this shoulder is slightly greater than the thickness of the sheet material from which the lever arm is made. This assembly is secured by means of a screw 40 which is fitted through the hole 38 and threads into a suitably tapped hole in the switch panel. The head assembly of the screw bears against the end of the cylindrical shoulder 37 and thereby screws the post to the switch panel. Post 36 is of hexagonal cross section so that a Wrench may be applied thereto for turning the post. If the eccentricity is downward as illustrated in Fig. 2, rotation of the post clockwise or counterclockwise will laterally shift the pivot point of lever arm 33 to the left or to the right to thereby provide for the proper location of the ends of the hooks 33a and 33b with respect to leaf springs 21 and 21'.

Only a fragmentary portion of the mechanism is illustrated in Fig. 4, to demonstrate the modification which may be made to the above-described structure. In this embodiment the lever arm 42 which is adapted to be pivotally mounted in the same manner as the lever arm 33 is, provided with a hooked lower extremity 4217. A link- 17a'which is. similar functionally to the links 17 and 17 is providedwith an upwardly turned flange 17b atone side thereof against which the end of hook 421) beats. A similar arrangement would be practiced on the link of the upper lever system. Thus instead of picking displacement from the leaf springs 21 and 21', the movement or displacement may be taken from a link such as 17a. Alternatively a slot (not shown) may be punched through a link such as 17a adjacent the V-shaped notch in the end thereof and the modified end of a lever arm inserted therethrough to again pick oif such movement of the link and transfer this movement to the other lever system. Numerous other variations in these concepts may be obtained with relatively simple expedients.

Although but two embodiments of this invention have been described, it will be appreciated that numerous other structural variations may be made without departing from the spirit and scope of the teachings of this invention. Accordingly it is intended that the foregoing disclosure and the showing made in the drawings shall be considered only as illustrative of this invention and not interpreted in a limited sense.

I claim as my invention:

1. An interlocking mechanism for a pair of levers for locking one lever upon movement of the other in a given direction, which comprises, a pair of lever systems, each including a lever having a pivot mounting, a link pivotally connected to the lever at a link pivot point on the lever spaced from the pivot mounting therefor, and a movable member movably supported adjacent the lever and connected with said link at a point spaced from the link pivot point on the lever; each link being normally angularly disposed with respect to the respective levers in an angular position removed from that angular position in which the link is effective to lock angular movement of the connected lever, angular movement of each lever in said given direction, through the respective links moving the respective movable members away from locking position, an interlock lever connected between the lever systems, a rotatable pivot mount having an eccentric pivot thereon eccentrically disposed of the axis of rotation of said pivot mount and pivotally mounting said interlock lever at a point between said lever systems, said pivot mount laterally displacing said interlock lever upon rotation of said pivot mount and providing adjustment of the connection of said interlock lever with each lever system, said interlock lever moving the link of one lever system to locked position upon movement of the lever of the other lever system in said given direction.

2. An interlocking mechanism for a pair of levers for locking one lever upon movement of the other in a given direction, which comprises, including a lever having a pivot mounting, a link pivotally connected to the lever at a link pivot point on the lever spaced from the pivot mounting therefor, and a flat leaf spring supported at one end adjacent the lever and having the free extremity thereof connected with said link at a point spaced from the link pivot point on the lever, said leaf spring being disposed edgewise with respect to the link, each link being normally angularly disposed with respect to the respective levers in an angular position removed from that angular position in which the link is effective to lock angular movement of the connected lever, angular movement of each lever in said given direction through the respective links deflecting the free extremities of the respective leaf springs away from locking position, an interlock lever connected between the lever systems, a rotatable pivot mount having an eccentric pivot thereon eccentrically disposed of the axis of rotation of said pivot mount and pivotally mounting said interlock lever at a point between said lever systems, said pivot mount laterally displacing said interlock lever upon rotation of said pivot mount and providing adjustment of the connection of said interlock lever with each lever system, said interlock lever moving the link of one lever system to locked position upon movement of the lever of the other lever system in said given direction.

a pair of lever systems, each i til 3. An interlocking mechanism for a pair of levers for locking one lever upon movement of the other in a given direction, which comprises, a pair of lever systems, each including a lever having a pivot mounting, a link pivotally connected to the lever at a link pivot point on the lever spaced from the pivot mounting therefor, and a movable member movably supported adjacent the lever and connected with said link at a point spaced from the link pivot point on the lever; each link being normally angularly disposed with respect to the respective levers in an angular position removed from that angular position in which the link is effective to lock angular movement of the connected lever, angular movement of each lever in said given direction through the respective links moving the respective movable members away from locking position, and a lever arm having pivot means pivotally mounting said lever arm between said lever systems, the ends of said lever arm being connected with said movable members, movement of one movable member by the lever and link connected thereto in said given direction angularly displacing said lever arm, said angular displacement of said lever arm moving the other movable member in a direction to move the link connected therewith to locking position, and means providing adjustment of said pivot means to laterally displace said lever arm to adjust the connection of said ends of said lever arm with said movable member.

4. An interlocking mechanism for a pair of levers for locking one lever upon movement of the other in a given direction, which comprises, a pair of lever systems, each including a lever having a pivot mounting, a link pivotally connected to the lever at a link pivot point on the lever spaced from the pivot mounting therefor, and a movable member movably supported adjacent the lever and connected with said link at a point spaced from the link pivot point on the lever; each link being normally angularly disposed with respect to the respective levers in an angular position removed from that angular position in which the link is effective to lock angular movement of the connected lever, angular movement of each lever in said given direction, through the respective links moving the respective movable members away from looking position, and a lever arm having pivot means pivotally mounting said lever arm between said lever systems, said lever arm having the ends thereof connected with points on said links displaced from the link pivot points on said levers, angular movement of one link upon movement of the connected lever being effective to angularly displace said lever arm and move the other link to locking position and means connected with said pivot means and providing adjustment of said lever arm in a lateral direction to adjust the connection of the ends of said lever arm with said links.

5. An interlocking mechanism for a pair of levers for locking one lever upon movement of the other in a given direction, which comprises, a pair of lever systems, each including a lever having a pivot mounting, a link pivotally connected to the lever at a link pivot point on the lever spaced from the pivot mounting therefor, and a flat leaf spring supported at one end adjacent the lever and having the free extremity thereof connected with said link at a point spaced from the link pivot point on the lever, said leaf spring being disposed edgewise with respect to the link, each link being normally angularly disposed with respect to the respective levers in an angular position removed from that angular position in which the link is effective to lock angular movement of the connected lever, angular movement of each lever in said given direction through the respective links deflecting the free extremities of the respective leaf springs away from locking position, and a lever arm having pivot means pivotally mounting said lever arm between said lever systems, the ends of said lever arm being connected with said leaf springs, movement of one leaf spring by movement of the associated lever in said given direction angularly displacing said lever arm and moving the other leaf spring to angularly displace the link connected thereto toward locking position, and

.7 means -connected with said pivot means providing lateral displacement of said lever arm to adjust the connection of the ,ends of said lever arm with said links.

6. Ameehanical interlock for a pair of relatively movable dcvices operable to lock one device against movement in response to movement of the other device, which comprises, a pair of levers respectively having a pivot mounting and a connection operable to efiect pivotal movement thereof in response to movement of the respective devices, a pair of locking links, each of said levers having one of said locking links pivotally connected thereto at a link pivot point on the lever displaced from the pivot mounting, a movable member movabl-y supported in a normal position adjacent each lever, which normal position is displaced from the line of action of the force through said link pivot point when said lever is rotated, each link being connected to the associated movable member and moving the associated movable member from said normal position in one direction away rforn said line of action when the associated lever is actuated by the connected movable device, an interlock lever connecting the movable members, a rotatable pivot mount having a rotatable pivot thereon eccentrically disposed of the axis of rotation .of

said pivot mount and pivotally mounting said interlock lever at a point between said movable members, said eccentric pivot laterally displacing said interlock lever upon rotation of said pivot mount and providing adjustment of the connection of said interlock lever with said movable members, said interlock lever moving one movable mem ber toward said line of action to lock the connected lever when the other movable member is moved in said one direction by the lever and link connected thereto.

References Cited in the file of this patent UNITED STATES PATENTS 665,127 Parmelee, Jan. 1, 1901 2,525,501 Taylor Oct. 10, 1950 2,593,288 Fisher Apr. 15, 1952 2,604,796 Freese July 29, 1952 2,680,971 Kreiner June 15, 1954 

